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why we see one side of the moon

Since launching in 1990, the has captured some of our corner of the universe, from neighboring planets to distant nebulae. An updated picture released by the European Space Agency shows two galaxies colliding 350 million light-years away, a process the ESA has been tracking for 52 years, reports. Galaxies are constantly changing shape and creeping through space. When two of these massive networks cross paths, their stellar material begins to intermingle, and they eventually merge into one entity under the force of gravity. In this image depicting two barred spiral galaxies in the Cetus constellation, the two nuclei are still separate, but the explosive merging process has already been set in motion. Long tidal tailsstreams of gas, dust, and starsfeather out from the top of the cluster. The bright blue patches indicate "stellar nurseries" where gas and dust stirred together by gravity are producing new stars.

The photograph was first released in 2008, but this latest version has been updated using Hubble's Advanced Camera for Surveys (ACS) and the Wide Field Camera 3 (WFC3). According to anPESAP, the galaxies "are like a natural experiment played out on a cosmic scale, and by cataloguing them, astronomers can better understand the physical processes that warp spiral and elliptical galaxies into new shapes. " Galactic mergers are a vital part of the evolution of the universe: Even the Milky Way is on course to crash into a neighboring galaxy 4 billion years down the road. But the process, though violent, is slow-moving. It will be millions of years before these two galaxies in Cetus settle down into one. [h/t ] The image of the Moon here is drawn as is normally shown on maps, that is with north on top and west to the left. Astronomers usually turn the map over to have south on top, as to correspond with the view in most telescopes which also show the image upside down.

West and east on the Moon are where you would expect them, when standing on the Moon. But when we, on Earth, see the Moon in the sky, then the eastwest direction is just reversed. When specifying coordinates on the Moon it should therefore always be mentioned whether (or rather ) coordinates are used or coordinates. The actual orientation you see the Moon in the sky or on the horizon depends on your geographic on Earth. In the following description a few typical cases will be considered. On the north pole, if the Moon is visible, it stands low above the horizon with its north pole up. In mid northern latitudes (North America, Europe, Asia) the Moon rises in the east with its northeastern limb up (Mare Crisium), it reaches its highest point in the south with its north on top, and sets in the west with its northwestern limb (Mare Imbrium) on top.

On the equator, when the Moon rises in the east, its N S axis appears horizontal and Mare Foecunditatis is on top. When it sets in the west, about 12. 5 hours later, the axis is still horizontal, and Oceanus Procellarum is the last area to dip below the horizon. In between these events, the Moon reached its highest point in the and then its selenographic directions are lined up with those on Earth. In mid southern latitudes (South America, South Pacific, Australia, South Africa) the Moon rises in the east with its southeastern limb up (Mare Nectaris), it reaches its highest point in the north with its south on top, and sets in the west with its southwestern limb (Mare Humorum) on top. On the south pole the Moon behaves as on the north pole, but there it appears with its south pole up.